The present invention concerns an electromagnetic actuator according to the introductory part of the main claim. A device of this kind is universally known from the state of the art, FIG. 6 representing the applicant's internal state of the art but being used as generic and delimiting.
Specifically, the sectional view of FIG. 6 shows an electromagnetic actuator which is typically designed to actuate a hydraulic or pneumatic valve as an actuating partner and which has an armature unit guided in a housing 10 and consisting of an armature body 12 and an armature plunger 14 seated thereon. With its left engaging end, the armature plunger 14 actuates the actuating partner.
In a manner not shown, the arrangement (as otherwise known) is surrounded by a coil support together with coil device, and when current is passed through the coil device the armature unit 12, 14 is moved (against the force of a return spring, not shown, typically constructed on the side of the actuating partner) into the left position shown in FIG. 6. When the current through the coil device is switched off or the polarity of the control signal is reversed, the armature unit then moves back into the right stop position (referred to FIG. 6), then abutting against a plunger element 16 (so-called emergency or manual plunger for manually actuating the armature by e.g. pushing on an engaging end 18). As can be seen from FIG. 6, the emergency manual plunger (typically made as a rotatable part) is held centrally in a stop element 20 (in a sealing relationship by means of an inner ring seal 22), the stop element 22 (which is in turn sealed off from a hollow cylindrical inner wall of the housing 10 by means of an outer ring seal 24 and non-releasably attached to the housing by means of a crimped portion 26 of the end of the housing, which engages in an annular groove 28 in component 20) being constructed as a rotatable part as well. In addition the rotatable part 20 has at the end a suitably applied external thread 30 which is provided for cooperation with a sleeve nut (not shown in FIG. 6) with which then e.g. the arrangement shown can be suitably attached or fixed at a point of application.
The device shown, which is used as generic, has numerous drawbacks which prove to be unfavourable and in need of improvement particularly with a view to favourable manufacture in large series; thus first of all the design of the manual plunger 16 and of the stroke-limiting stop element 20 as rotatable parts is inherently elaborate and therefore expensive. Also the assembly shown is disadvantageous with respect to internal pressure or fluid equalisation (mainly concerning oil flowing in the assembly): as illustrated for example by the longitudinal bore 32 shown in the sectional view of FIG. 6 and running axially/eccentrically in the armature body 12 (which bore is then in flow communication with a channel 34 surrounding the solid armature plunger 14 and substantially produced by play and opening towards the outlet end 36), fluid conduction for the purpose of equalising pressure between the right end stop and the end 36 is problematic and, for example with respect to precise guiding of the armature, also in need of improvement.